A band of abnormally warm water, shown in red, spans the Atlantic Ocean
from
Africa to Central America in this sea surface temperature image from
August 5, 2005. The warm
region—Hurricane Alley—is the birthplace of hurricanes in
the
Atlantic, and unusually warm waters means that storms have plenty of
fuel
to develop.

Hurricane Alley is heating up, and temperatures are warmer than
average
(1985-1997). Not only does this mean that hurricanes may be more likely
to
form, but the weather pattern that is causing the ocean to warm can also
steer storms straight for Florida. The pattern may also be responsible
for
the July 2005 heat wave that swept across the Midwestern United
States.

Normally, a large area of high atmospheric pressure sits firmly
entrenched over the Atlantic Ocean. Called the Bermuda or Azores High
because the center of the high pressure system shifts back and forth
between the two islands, the system stirs air around the North Atlantic
in a giant clockwise circle. A high-pressure system pushes air down
toward the surface, causing it to warm and dry out. In the warmer, drier
air, fewer clouds form to shield the ocean from the sun, allowing water
temperatures to rise.

In the summer of 2005, the Bermuda High has been extended to the
south and west, letting Hurricane Alley bake under relatively clear
skies. The result is the streak of warm water seen in this image. Since
one of the ingredients necessary for a hurricane to develop is warm
ocean water (at least 28 degrees Celsius or 82 degrees Fahrenheit), this
streak could lead to more hurricanes during the 2005 season. On August
2, the National
Oceanic
and Atmospheric Administration (NOAA) increased their predictions
for
the 2005 season, warning that 11-14 storms may form between August and
November in addition to the 9 that have already pushed through the
Atlantic.

The south- and westward extension of the Bermuda High affects more
than sea surface temperatures. Remember, the Bermuda-Azores High spins
the air over the Atlantic in a giant, clockwise circle. As hurricanes
develop in Hurricane Alley, along the bottom side of the
#8220;clock,” they travel west around the edge of the high
pressure system. Often, the clockwise circulation pattern will bend
storms northward into
the Atlantic before they make landfall on the East Coast. But with the
edges of the high pressure system extending farther south and west than
normal, storms can run into the United States as they make their
northward turn around the high-pressure system. In 2004, with the
Bermuda High in a similar position, a record four hurricanes pounded
Florida in rapid succession.

The weather pattern could also be connected to the high temperatures
across the Midwestern United States. Just as the Bermuda High can sweep
hurricanes from the Atlantic into the United States, it also drags warm
tropical air northward. Because the edge of the high sits farther west
than normal (closer to the U.S. East Coast), hot humid air is
circulating farther inland, leaving the Midwest hot and sticky.

This image was created from data gathered by the Advanced Microwave
Scanning Radiometer-EOS (AMSR-E) on NASA’s Aqua satellite on
August
5, 2005. AMSR-E was provided to the Aqua program by the Japanese
Aerospace
Exploration Agency (JAXA).